Cleaning appliances such as vacuum cleaners are well known. The majority of vacuum cleaners are either of the “upright” type or of the “cylinder” type (called canister or barrel machines in some countries). Cylinder vacuum cleaners generally comprise a main body which contains a motor-driven fan unit for drawing a dirt-bearing air flow into the vacuum cleaner, and separating apparatus, such as a cyclonic separator or a bag, for separating dirt and dust from the air flow. The dirt-bearing air flow is introduced to the main body through a suction hose and wand assembly which is connected to the main body. The main body of the vacuum cleaner is dragged along by the hose as a user moves around a room. A cleaning tool is attached to the remote end of the hose and wand assembly.
For example, WO 03/068042 describes a cylinder vacuum cleaner having a chassis which supports cyclonic separating apparatus. The vacuum cleaner has two main wheels, one on each side of a rear portion of the chassis, and a castor wheel located beneath the front portion of the chassis which allow the vacuum cleaner to be dragged across a surface. Such a castor wheel tends be mounted on a circular support which is, in turn, rotatably mounted on the chassis to allow the castor wheel to swivel in response to a change in the direction in which the vacuum cleaner is dragged over the surface. The separating apparatus comprises an air inlet through which air can enter the separating apparatus in a tangential manner, and an air outlet which is located on a rear wall of the separating apparatus for conveying air to a fan unit for drawing an air flow through the vacuum cleaner.
PCT/GB2010/050418 describes a cylinder vacuum cleaner having a generally spherical rolling assembly connected to the chassis for improving the maneuverability of the vacuum cleaner over a floor surface. The rolling assembly comprises a body and a pair of dome shaped wheels connected to the body. The chassis extends forwardly from the body of the rolling assembly, and includes a pair of wheels for steering the vacuum cleaner and for supporting the rolling assembly as the vacuum cleaner is maneuvered over a floor surface. The chassis also includes a support for supporting cyclonic separating apparatus of the vacuum cleaner. The separating apparatus includes two cyclonic separating stages and a filter assembly located downstream from the cyclonic separating stages.
A fan unit for drawing an air flow through the vacuum cleaner is located within the rolling assembly. Air is conveyed from the separating apparatus to the rolling assembly by a duct which extends from an upper surface of the separating apparatus to an upper surface of the body of the rolling assembly. The support for supporting the separating apparatus is biased so as to urge the separating apparatus upwardly towards the duct so that an air outlet of the filter assembly is urged against the air inlet of the duct to maintain an air-tight seal therebetween.
The inventors have found that depending on the size of the separating apparatus, the variation in the weight of the separating apparatus between a loaded state, in which the separating apparatus is filled with dirt and other detritus separated from the air flow, and an unloaded state can be relatively large. When the separating apparatus has a relatively large volume, a relatively high spring force may be required to maintain the air tight seal between the separating apparatus and the duct over the loading range of the separating apparatus. This can in turn result in the separating apparatus applying an undesirably high force to the duct when it is in its unloaded state, which over a prolonged period of time could result in damage to the duct or the separating apparatus, or to any seals made between the separating apparatus and the duct.